1. Technical Field
This invention relates to the field of blood sampling and testing, and more particularly concerns making a hematocrit determination from a blood sample, especially before giving blood as a blood donor.
2. Background of the Prior Art
Before you are allowed to donate blood, like to the Red Cross, a hematocrit determination must be made, which is the ratio of the volume of red cells to the total volume of the blood sample.
One method of testing the blood has been to check the specific gravity of the blood by putting a drop of blood into a copper sulfate solution. If the drop of blood falls to the bottom, it means that the blood has a higher specific gravity than the copper sulfate solution. If the blood sample floats, it means that the blood should be checked further.
In testing blood to make a hematocrit determination, the ratio of volume of red cells to the total volume of the blood sample, it is conventional to take a capillary blood sample tube, prick the finger or ear of a patient to produce a drop of blood, draw the blood into a blood sample tube by capillary action, and send the blood sample out to a laboratory which makes the hematocrit determination, and reports back to the doctor or blood sample technician who had ordered the test. This procedure may take several days, which is undesirable.
Accordingly, it has been a problem to provide quicker and cheaper ways of making a hematocrit determination. This search has been intensified with the advent of desk-top portable centrifuges which have now become available.
In order to shorten the time necessary to make a hematocrit determination, it is now possible to provide the technician who takes the blood sample with a portable centrifuge so that the technician can immediately make a hematocrit determination. This is very useful when the patient is a potential blood donor because the technician can make an instantaneous determination before the blood donor gives blood, and the blood donor is not left sitting around for a long period of time while awaiting the hematocrit determination.
In making this instant hematocrit determination, one prior art procedure is to prick the finger or ear of a potential blood donor, or patient, to produce a drop of blood, draw the blood into a blood sample capillary tube by capillary action, place the filled sample tube into a chamber in a holder with the bottom end of the tube in contact with a rubber seal or plug to hold the blood from discharging from the bottom of the tube, place the holder into a centrifuge, turn on the centrifuge and separate the blood into a column with a red cells column portion at the bottom of the tube, a white cells column portion in the middle of the tube, and a blood plasma column portion at the top of the tube. Then the hematocrit determination is made immediately by dividing the length of the red cells column portion by the total length of the blood column.
This on-the-spot hematocrit determination procedure requires use of device which has two separate parts, the sample tube and the holder which receives the sample tube, and requires the insertion of the bloody blood sample tube into the holder. This can be awkward and cause a bloody mess. Also, the bottom end of the sample tube is supported by a bottom seal made of resilient rubber which pushes upwardly into the hollow bore of the sample tube to form a nipple therein which pushes a top portion of the blood upwardly to extend above the top end of the capillary sample tube. Then when the centrifuge spins, the top portion of blood which is above the end of the capillary sample tube is struck by air and is vaporized. This is undesirable.